This invention relates to a method of mixing a liquid and a powdery component by vibration of a mixing chamber containing the components, particularly for dental purposes, in which the liquid component, tightly enclosed in a foil bag, is inserted in the mixing chamber and exposed to the mixing vibration, the strength of the foil bag being predetermined such that it releases its contents under the action of the mixing vibration. The invention also relates to a mixing capsule and a portion package for practicing the method.
In U.S. Pat. No. 4,306,651 to the present applicant which disclosure is incorporated herein by reference, a multicomponent capsule for dental purposes is shown wherein one component is freely contained in the mixing chamber of the capsule and the other component is contained in a foil bag and thereby separated from the one component until the foil bag is destroyed by the mixing vibration. Obviously it is sufficient to enclose merely one component in a bag so as to ensure chemical separation during the storage period. The use of a multicomponent capsule for storage and for a single mixing operation involves a certain expenditure, which can be avoided where the dentist places silver powder as well as, by means of a dosing apparatus, a corresponding quantity of mercury into a mixing capsule for multiple use, closes the capsule and subsequently mixes the components in a vibration apparatus. While this method is less expensive, inexact dosages may result more readily than with a mechanical predosing, and the physician is exposed to the immediate influence of the mercury.
The present invention concerns the problem of combining the simplicity of the method as known from the use of disposable capsules with the low expenditure involved in the repeated use of the capsule.
The solution according to the invention resides in the fact that the powdery component is also enclosed in a separate foil bag which is exposed to vibration and opens under the action of the mixing vibration, with the foil bag consisting of a material having a specific gravity several times lower than that of the powdery component.
The enclosure of both components in respective foil bags permits their optional use, irrespective of whether they are supplied a priori in a disposable capsule or whether they will be inserted by the dentist into a mixing capsule to be used, if necessary, several times. Furthermore, it permits an easy and simple dosing by inserting in each case such a number of foil bags with the components into a mixing capsule as it corresponds to the desired amalgam amount.
It could not be expected that powder would liberate itself sufficiently completely from a foil bag which opens under the mixing vibration since it cannot be expected even of the liquid component under certain conditions. For example, there is the possibility that mercury will not be discharged completely from a sealed metal foil bag as disclosed in U.S. Pat. No. 4,182,447. If the complete emptying of the foil bag appears not to be ensured even with liquids under certain conditions, then this could much less be expected as regards the storage of a powder in a foil bag. It is more surprising that the complete discharge of the powdery component is achieved if, according to the present invention, the specific gravity of the bag material is several times lower than that of the powder. It may be assumed that this effect is due to the fact that, in accordance with the law that "force equals mass times acceleration", the forces exerted under the vigorous vibration accelerations on the substances contained in the capsule are considerably smaller regarding the specifically lighter bag material than regarding the powder particles so that the latter are separated from each other by the very different forces acting on them. It may also be of importance in this connection that under vibration conditions the powder does not behave as a solid but similar to a liquid. This is due to the fact that the powder particles get into a relative motion with respect to each other, wherby air layers are enclosed between them which terminate the solid connection and put the powder on the whole into a so-called fluidized state, which is known and being used in another technical field, namely that of the mechanical conveying and handling of powdery material.
It can easily be determined by experiments by how many times the specific gravity of the powder must be greater than that of the bag material. There is to be achieved a density ratio, relative to the solid powder material, of at least 5 and preferably of more than 8.
The invention relates furthermore to a mixing capsule for carrying out the stated method of the vibration mixing of several components contained therein, particularly for dental purposes. The mixing capsule contains in a mixing chamber a liquid component tightly enclosed in a foil bag for releasing said component under the action of mixing vibration and a powdery component. The powdery component is contained in a separate foil bag opening under the action of the mixing vibration with the foil bag consisting of a material having a specific gravity several times less than that of the powdery component by a factor of at least 5 and preferably more than 8.
Finally, this invention relates to a portion package for silver powder or the like powdery dental material intended for vibration mixing in a dental mixing capsule. In the package, the powder is enclosed in a foil bag, the material of which is specifically several times lighter than the powder and the strength of which is predetermined such that it opens under the action of the mixing vibration in the mixing chamber of the dental mixing capsule.
The enclosure of the powder, particularly of the silver powder, in a foil bag has the great advantage that the portion size can be predetermined with great exactness. This advantage exists also if the powder is present in a briquetted form. It is known to make the silver powder available to the dentist in the form of compressed tablets, which disintegrate to powder under the action of mixing vibration and are industrially adjusted to a specific weight portion. Since these tablets are rubbing against each other during transport and use, for instance when taking out individual tablets, there occurs a constant loss in weight by abrasion which may lead to an error in the weight ratios in the amalgam preparation. Such loss by abrasion is prevented by the enclosure of the silver in foil bags.
According to a further feature of the present invention, portion packages of the dental material components to be used together can be connected to each other. This presents not only the advantage that the use is simplified since in each case only one portion package with both components needs to be inserted in the mixing capsule but also the portioning becomes more reliable since no mistakes can occur in the coordination of component amounts suited to each other. Additionally, several portion packages can be inserted in the mixing capsule at a time, such as for a large tooth filling there is required an amalgam amount greater than that provided by one portion package.
The connection of the two individual portion packages to a common portion package can be achieved in a simple way, e.g., by adhesion bonding. According to another feature of the present invention, the connection between the individual portion packages is obtained in that at least one foil is involved in the formation of both portion packages. Preferably, even both portion packages are formed integrally by a pair of foils, which are welded together in forming two separate portion pockets.
According to a further embodiment of this invention, two cover foils are welded together with a central foil, in forming two portion pockets situated on both sides of the central foil.
The destruction of the foil bag containing the liquid component is facilitated by the powdery component being packed in a foil bag and combined as a unit with the liquid bag, since the entire powder material substantially simultaneously exerts impact on the liquid bag and thus a stronger effect thereon than simply a powder distributed in the entire space.
There may be provided devices which improve the opening of the foils under the action of the mixing vibration and/or the mixing effect, for example a pestle, which may also be contained in the portion package, or edges or prongs projecting inwards from the wall of the mixing chamber.
If a capsule is to be used repeatedly for the preparation of amalgam, it has to be cleaned between the individual applications or at least from time to time. Furthermore, it has to be considered a disadvantage that the prepared mixture must be taken out of the capsule in a relatively complicated way, in which respect also the remainders of the consumed package, likewise contained in the capsule, can be inconvenient. Such disadvantage can be avoided in accordance with the present invention in that the package foil, destructible by the action of the mixing vibration, together with the portion chambers separated therefrom and including the dental material components, is enclosed by a package casing not destructible by the action of the mixing vibration.
After the mixing process, the mixed material is not contained in a free form within the mixing chamber of the mixing capsule but is still enclosed by the foil bag, wherein merely the inner separating foil has been destroyed. One can therefore simply take the closed portion package out of the mixing capsule, tear it open and take out the mixture by a spatula or squeeze it out between two fingers. Thereby the removal of the mixture is substantially simplified, and it is achieved without special measures that the mixture remains hygienic.
The arrangement of the package foil destructible by the mixing vibration with respect to the nondestructible packaging casing can be different. In one advantageous embodiment there are provided for example two foil bags, one of which freely encloses as a convering foil bag the first dental material component as well as the destructible foil bag containing the second dental material component. In accordance with another expedient embodiment, it is provided that two foils, together forming the covering foil bag, are welded together on both sides of the destructible foil either to the latter or to each other.
After mixing, the outer package casing which is not destructible by the mixing vibration forms a container for the mixed dental material. In order that the container can be handled more easily, it can be formed according to the invention as a semi-flexible, cup-like package portion. The term semi-flexible is to mean that the container retains its cup shape in a more or less deformed state, even if it is held between the fingers in order to be emptied. Its cup shape facilitates the removal of the mixed material.
Additionally, it may be provided according to the present invention that the package casing is provided with an opening device. An opening device is understood to mean those elements or formations which enable or facilitate the opening process. This includes, for example, gripping lugs projecting outwards from the portions forming the actual package casing so as to allow, for the purpose of opening, a gripping thereof and the exertion of a force. Furthermore, this includes ideal tearing points and notches in the welding edge at which the opening tear may be started.
The portion package according to the present invention can enclose the dental material components without a substantial empty space so that the mixing forces created upon the impact of the portion package during the mixing vibration at the ends of the mixing capsule will be transferred, without being damped, onto the dental material components to be mixed. This applies particularly if a flexible material is used for the nondestructible package casing, which completely transmits the forces to the dental material. Instead of this, it may, however, also be provided that the portion package includes a certain empty space permitting a certain vortexing. This applies particularly if the package casing consists wholly or partially of a semi-flexible or a stiffer material.
It may also be expedient that the portion package contains a pestle, i.e., a body of, for instance, glass, ceramics, synthetic material, which, due to its movement within the portion package, caused by the mixing vibration, assists in the mixing of the components.
It is not necessary that the two component bags are inserted in a mixing capsule only at the dentist and immediately prior to use, but the invention rather presents also the advantage that the filling of the capsule becomes independent of the dosing and encasing of the components. Finally, there is achieved the advantage that it is not necessary to tightly close the capsule, even if the latter is intended for long-term storage, since the components in their bag packages can be sufficiently sealed against atmospheric influences and it can be prevented that, due to evaporation, they emit poisonous influences into the atmosphere.
The foil packages may be provided with imprints, i.e., with statements as required under the drug law, such as the name of the manufacturer, weight, durability, data of filling, specification of the materials, etc. The individual foil packages can be lined up as double packages or individually within a strip of similar packages and can be separable from each other and, if necessary, from the strip section provided with the information by perforation or predetermined breaking points, respectively.
The invention presents considerable price advantages over the known disposable capsules, which mostly have to be additionally prepared for mixture by turning, pressing or screwing. The encasing of the amalgam powder in foil bags can also be advantageous over the processing in the form of tablets since the latter first have to be compressed, which involves costs. Moreover, it can be disadvantageous for some amalgam powders to be compressed to tablets. Finally, the abrasion of the tablets may lead to differences in weight. Compared with the use of automatic mixers, the invention involves the advantages of a greater exactness, that amalgams of any kind can be used, that no maintenance of the apparatuses is required, and that the dentist is not exposed to mercury vapor.
The portion package of the components to be mixed can be inserted in the mixing capsule at any point of the chain between production, storage and use.
In the context of the invention both the mixing capsule and the vibration mixers used for dental purposes can be considered to be known. The mixing capsules are elongated containers closed by a removable lid and having a length in the order of magnitude of 3 cm and a diameter in the order of magnitude of 1 cm. The mixers are formed such that the mixing capsules inserted therein can be reciprocated in their longitudinal direction at a frequency of, e.g., 300 Hz so that the material contained in the interior of the capsule (mixing chamber) is flung to and fro between the end walls of the mixing chamber. The volume of the material amounts to only a very small part of the volume of the mixing chamber. Typical amalgam portions as they are prepared by the dentist in one mixing operation lie between 0.5 g and 1 g.
With respect to foil materials, there are particularly suitable synthetic materials, e.g., a polyethylene foil of a thickness in the order of magnitude of 0.05 mm.